Anybody slowing down from 150+ mph very quickly??

[David Pozzi]

With your power level and car weight, you are right to worry about your brake system. Having a brake failure on a high speed track could endanger you and others on the track. Repeated laps will heat up all the systems in your car so coolers are needed for almost everything. I've seen power steering heat failures, so include a PS cooler too. A good aftermarket box with increased stiffness is what you need. Reducing pressure on your current box will show up in lack of boost when parking at low rpm's, not what you want.

My wife's 425hp 73 Camaro with the 13" Baer brakes went through the original pads in the first open track weekend. We swapped in better pads and increased braking distances and they are lasting much better, but there is no way we can brake near the limits of tire traction for repeated laps. We get some brake fluid related fade when we brake very hard which tells me our caliper temps are running very high. Our next step is to add brake ducting which will help a lot. We used the Valvoline fluid at first, but Motul or Willwood synthetic has a higher temp rating.

For your car I'd strongly suggest using the largest rotors you can fit and a good four piston caliper. The C5 brakes are not going to fit in your 17" wheels. Add brake ducts and brake early for the turns, enter the turns a bit slow and take a late apex to reduce the chances of going off course on corner exit. At the end of the track session, (checkered flag) -slow down and stay off the brakes, allow them to cool down or you will melt the seals out of the calipers when you stop. Cool off laps are for cooling off, not getting in an "extra" hot lap!

RA is a very fast track, you need to upgrade your steering box, springs shocks and antiroll bars, etc. It will make the car much easier to drive on the track.
David